Device for releasing a spear shaft of a spear gun for scuba diving or the like

ABSTRACT

A device is provided for releasing a spear shaft of a spear gun for scuba diving or the like. A latch element of the shaft is formed on a first lever pivotally connected at its front end to a screw attached to and integrally with a frame of the gun, and is elastically maintained in a resting position. A trigger of the gun includes an abutment portion forced elastically against the front end of the first lever extending forward of a convex upper surface intersecting a concave surface at an edge that traces a first circular trajectory when the trigger is rotated. A second lever is rotatably connected to the frame, the front end of the second lever being movable along a second circular trajectory intersecting the first circular trajectory. An arm of the second lever extends so as to intersect the trajectory of the spear shaft when it is loaded in the gun, such that the shaft abuts the latch element first, thereby moving the first lever away from its resting position, until it engages a shaped cavity of the shaft, and subsequently abuts the arm of the second lever, causing it to turn until it abuts the first lever in line with the latch element, simultaneously raising its front end up to and against the convex surface of the trigger. The front end of the first lever is slidingly connected to the screw, such that the first lever may be adjustably displaced, thereby varying the force applied by the second lever on the trigger.

FIELD OF THE INVENTION

The present invention relates generally to underwater activities and, more particularly, to spear guns for use in fishing and underwater hunting.

BACKGROUND OF THE INVENTION

Conventional spear guns, such as those utilized in scuba diving, typically comprise a frame having a longitudinally elongated body fit at a rear end with a grip and a trigger. The trigger is pulled to launch a spear attached to a front end of a shaft, mounted slidingly on the elongated body of the frame. The rear end of the shaft is usually connected to a string line for retrieval of the spear and any prey that may have been snagged by the diver.

The propulsive force of the spear is provided by a pair of cables made of an elastic material that are stretched and hooked onto the shaft of the spear when the diver loads the gun, then the spear is released when the trigger is pulled, converting the elastic energy accumulated by the elastic cables into kinetic energy in the spear shaft.

The kinematic mechanism that enables the diver to shoot the spear by means of the trigger generally comprises a lever hinged onto the frame and presenting a latch element at one end that engages in a notch at the proximal end of the spear shaft when the spear on the gun is loaded so as to withstand the pulling force exerted on the shaft by the elastic cables. During the movement used to load the spear gun, the proximal end of its shaft abuts against a radial appendage on the lever, thereby inducing its rotation, as a result of which, in addition to the latch element engaging in the notch on the shaft, the opposite end of the lever elastically engages within a seat in the trigger formed on the side opposite its operating arm. The disengagement of the lever from the trigger, which is induced by a finger pulling on its operating arm, causes the shaft to be released from the latch element on the lever and the propulsive force of the elastic cables prevails. A kinematic chain of this type is shown, for instance, in U.S. Pat. No. 5,904,132.

In the spear fishing guns of the known type, the kinematic chains used to operate them, such as the one described above, do not allow for any adjustment of the stroke of the trigger and of the effort needed to pull it. In the event of the scuba diver's finger being scarcely sensitive due to limited experience, or for contingent reasons such as the use of very thick gloves, the spear may be released by accident if the stroke of the trigger is short. In other words, the problem of graduating the effort required to pull the trigger and/or adjusting the trigger's stroke is strongly felt and has yet to find a simple and safe solution.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a device for releasing a spear shaft of a spear gun for scuba diving or the like that allows the effort required to pull the trigger and/or the operating stroke of the trigger to be graduated in accordance with a selected diver's characteristics and needs.

A particular object of the invention is to provide a device of the aforementioned type wherein the force required to pull the trigger and/or the trigger's stroke can be adjusted quickly and easily by means of a kinematic chain that is not particularly complex from the point of view of its manufacture and assembly.

These objects are achieved with a device for releasing the spear shaft of a fishing gun for scuba divers according to the present invention, wherein the latch element is formed on a first lever, the front end of which is pivotally connected to a threaded stem fixedly attached to the frame of the gun and lying parallel to its longitudinal axis and elastic means are provided for keeping the first lever in a resting position, corresponding to the situation when the gun is not loaded, wherein the latch element abuts against a first shoulder integrally attached to the frame and is axially aligned with the spear shaft when it is prepared for loading on the elongated body of the frame. The trigger comprises an elastically-tensioned abutment portion for the front end of the first lever and extending forward from a convex upper surface intersecting a concave surface at an edge that traces a first circular trajectory as the trigger is rotated. A second lever pivotally connected to the frame at a point situated behind the latch element and below the front end of the first lever is also provided, the front end of the second lever being movable along a second circular trajectory intersecting the first circular trajectory. An arm of the second lever extends to intersect the trajectory of the spear shaft when the gun is loaded, whereby during the axial movement to load the spear, the spear shaft abuts against the latch element first, displacing the first lever from its resting position and occupying a loaded position wherein the latch element engages in the shaped recess in the shaft, and then it abuts against the arm of the second lever, making the latter rotate until it abuts against the first lever on at the latch element, simultaneously bringing its front end up against the convex surface of the trigger. The front end of the first lever is slidingly connected to the threaded stem, whereby the first lever is adjustably displaceable in the longitudinal axis direction to enable a variation in the point where the first lever rests on the second lever and the consequent force with which the front end of the second lever rests against the convex surface of the trigger.

BRIEF DESCRIPTION OF THE DRAWINGS

A specific, illustrative device for releasing a spear shaft of a spear gun, according to the present invention, is described below with reference to the accompanying drawings, in which:

FIG. 1 shows schematically a longitudinal section of a device for releasing a spear shaft of a spear gun, according to one aspect of the present invention, in a resting position, ready for loading with a spear;

FIG. 2 is a side view of the device illustrated in FIG. 1 in an intermediate position with the spear shaft being loaded;

FIG. 3 shows the device of FIG. 2 in a further intermediate position, with the spear shaft in a more advanced phase of loading;

FIG. 4 shows the device of FIG. 2 with the spear shaft in a fully loaded position;

FIG. 5 shows the device of FIG. 2 with the spear shaft in a position immediately after the trigger is pulled; and

FIG. 6 shows the device in a similar condition to that in FIG. 4, but with a different degree of adjustment to the effort necessary for a user to pull the trigger.

Still other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the adjectives “front” and “rear” refer to the orientation of the gun and refer to the left and right ends, respectively, as the spear gun appears in the figures. The adjectives “upper” and “lower” are used in an absolute sense and refer to the axis of longitudinal symmetry of the gun: the shaft and spear point are placed in the upper part of the gun, i.e. above its axis of symmetry, while the trigger is conventionally positioned in the lower part of the gun.

The illustration of the fishing gun for scuba divers is restricted to the elements comprising the release device according to the invention. The swivel pins for the articulation of the various component parts and the abutment elements for the moving parts are consequently only shown schematically, said pins and abutment elements being integrally attached to the gun frame, which is not shown in its entirety because it is structurally well-known to a person skilled in the art.

Referring now to the drawings and, more particularly, to FIGS. 1-6, there is shown generally a specific, illustrative device for releasing a spear shaft of a spear gun for scuba diving or the like, according to various aspects of the present invention. Illustrated in FIG. 1 is a cross-sectional view of two bushings S1 and S2, respectively, attached to and integrally with the frame, according to one embodiment. Abutment elements S4, S5, S6, S7 and S8 are also attached to and integrally with the frame and, consequently, are in a fixed position. In this manner, motion of moving parts or elements of the device is contained. Generally speaking, the movable elements of the device include a first lever L1, a second lever L2 and a trigger L3 articulated, respectively, around pins C1, C2 and C3, which are attached to and integrally with the frame.

In particular, the lever L2 and the trigger L3 have a flattened shape and lie substantially in the vertical plane of symmetry of the gun, passing through its longitudinal axis X, while the lever L1 comprises two symmetrical elements (only one of them shown in the figures), lying parallel to the plane of symmetry of the gun, the distance between them corresponding to at least the thicknesses of the lever L2 and of the trigger L3 so that the latter two elements can move without interfering with the movement of the lever L1.

The bushes S1 and S2 support a freely-revolving longitudinal threaded stem 10, the rear end of which (facing towards the right in the figure) is threaded inside and screws into a corresponding threaded hole in a transverse hub 11 from either side of which there project two transverse, symmetrical pins C1 (only one of which is shown in the figures) around which the two parallel and adjacent elements forming the first lever L1 are integrally articulated.

For the sake of simplicity, reference is made hereinafter to a single pin C1 as if the lever L1 consisted of a single element, a condition which may in fact constitute an alternative embodiment of the invention.

The axis of the threaded stem 10 lies substantially along the vertical plane of symmetry of the gun. Between the two bushes S1 and S2, the threaded stem 10 is provided with ring-shaped ribbing 12, the knurled lateral surface of which extends from the bushes S1 and S2 and enables the scuba diver to turn the threaded stem 10, thereby screwing or unscrewing its end in the threaded hole in the hub 11 and consequently displacing the axial position of the transverse pin C1 in the two directions indicated by the double line F1. In FIGS. 1 to 5, for instance, the pin C1 occupies its rearmost position, whereas in FIG. 6 the pin C1 is at the end of its forward stroke.

The lever L1 is hinged around the pin C1 at its front end (on the left in the figure), whereas it is fitted at its rear end with a freely-revolving wheel 14. The upper side of the rear end of the lever L1 terminates with a surface 13 designed to be pushed up against a shoulder S6, which is integrally attached to the gun frame. When in contact with one another, the surface 13 and the shoulder S6 define the end of the stroke of the lever L1 in its leftward-turning angular displacement, corresponding to the resting position of the lever L1, when the gun is not loaded.

The rear end of the second lever L2 is connected to the swivel pin C2, which is positioned to the rear of the wheel 14 and on a slightly lower level than the pin C1. The anticlockwise rotation of the second lever L2 is restricted by a shoulder S4. The pin C2 is wrapped with the turns of a spring M2, which terminate with two arms 15 and 16. The lower arm 15 is retained by a pair of fixed striker plates S5, while the upper arm 16 rests up against the wheel 14 of the lever L1, consequently pushing the surface 13 towards the shoulder S6. An upward-facing bracket 20 extends from the rear end of the second lever L2, the purpose of which will be explained with reference to the subsequent figures.

The front of the trigger L3, revolving around the pin C3, has a front concave surface 51, on which the scuba diver's finger comes to bear, a cylindrical and convex surface 39, whose axis coincides with that of the pin C3, and an upper-rear concave circular surface 38 with a radius of curvature equal to the distance between the axis of the pin C2 and the front end 18 of the lever L2. At a suitable angle of leftward rotation of the trigger L3, the concave circular surface 39 overlaps the trajectory T2 traced by the end 18 of the lever L2 as it moves rightwards. In said position of the trigger L3, the edge 40 common to the surfaces 38 and 39, which traces the trajectory T3, coincides with the point T, where the trajectories T2 and T3 intersect each other.

The clockwise rotation of the trigger L3 is restricted by a ledge 19 thereof resting up against the hub 11. There is also a spring M3 wrapped around the pin C3, with a lower arm 21 that pushes the trigger L3 to turn clockwise towards its end of stroke, wherein the ledge 19 rests up against the hub 11. The upper arm 22 of the spring M3 rests elastically against the lower edge of the lever L1, co-operating with the spring M2 in pushing the lever L1 into its endmost anticlockwise position, at which the surface 13 lies in contact with the shoulder S6.

The lower end 23 of a stem 24 is housed, with an angular slack, in a seat 41 in the lever L2, the upper end 25 of said stem being retained between striker plates S7 and S8. When the device according to the invention is in the resting position, shown in FIG. 1, said stem 24 is withdrawn, i.e. it does not extend beyond the striker plates S7 and S8, whereas it does project therefrom when spear is loaded on the gun, as shown in FIG. 4. Said upper end 25 serves as a transmission element for a string line (not shown) that links the rear end of the spear shaft 30 to the frame of the gun by means of a hole 32 in the shaft to which one end of the line is attached.

On the underside of the rear end 31 of the shaft 30 an elongated recess 33 with tapered sides 34 is formed, the purpose of which will be explained later on.

To load the gun, the shaft 30 is pushed along the gun in the direction of the arrow F2 so that its rear end 31 rests up against the wheel 14 of the lever L1, as shown in FIG. 2. In the condition shown in said figure, the levers L1 and L2, the trigger L3, the stem 24 and the springs M2 and M3 are still in the positions shown in FIG. 1.

As shown in FIG. 3, as the shaft 30 proceeds in its displacement along the loading trajectory in the direction of the arrow F2, it rides over the wheel 14, which is thus pushed downwards, overcoming the elastic force of the springs M2 and M3 and making the lever L1 rotate towards the right. In this position of the shaft 30, its rear end 31 rests against, but does not displace end of the bracket 20 on the lever L2. The lever L2, the trigger L3, and the stem 24 are still in the positions shown in FIGS. 1 and 2, while the angle coming between the two arms of the springs M2 and M3 is reduced due to the effect of the lever L1 being lowered to the end of its rightward turning stroke.

As it continues in its displacement in the direction of the arrow F2, the shaft 30 forces against the bracket 20, inducing the rightward rotation of the lever L2 until it reaches the end of its stroke, shown in FIG. 4. It should be noted that, in its endmost position, the shaft 30 does not necessarily remain in contact, at its rear end, with the bracket 20, as shown clearly with reference to the subsequent FIG. 6 too.

In the final position of the shaft 30, shown in FIG. 4, the wheel 14 rises inside the recess 33 due to the effect of the spring M2, reaching an intermediate position with respect to the terminal position of FIG. 1, so the lever L1 rotates partially leftwards, albeit without reaching the initial position shown in FIG. 1.

As the lever L2 turns to the right, driven by the rear end of the shaft 30, its front end 18 slides along the upper rear surface 38 of the trigger L3 making the trigger turn anticlockwise and overcoming the force of the spring M3, until the front end 18 of the lever L2 passes beyond the point 40, thus enabling the trigger L3 to return to the position shown in FIGS. 1, 2, 3 and 4, due to the effect of the spring M3. At the end of this rightward rotation towards the initial position of the trigger L3 (FIG. 1), the front end 18 of the lever L2 rests up against the surface 39 and occupies a position substantially parallel to the longitudinal axis of the gun, with its upper surface 50 coming up against the wheel 14.

The leftward axial tensile force coming to bear on the shaft 30 in its loaded position (FIG. 4) is transmitted via the surface 34 interfacing with the recess 33 to the wheel 14 and via its upper surface 50 to the lever L2. Said force generates an arm moment b1, balanced by the arm moment b2 generated by the force with which the end 18 of the lever L2 rests against the surface 39 of the trigger L3. The force needed to turn the trigger leftwards must consequently generate a torque capable of exceeding the one due to the force of friction at the point of contact between the end 18 of the lever L2 and the surface 39 of the trigger L3.

It should be noted that the rightward rotation of the lever L2 results in an upward displacement of the stem 24, the upper end 25 of which extends above the striker plates S7 and S8, thus enabling the string line connecting the shaft of the spear to the gun to be hooked to said end 25.

FIG. 5 shows the end of the stroke of the trigger L3 under the effect of the force R4 exerted by the scuba diver's finger on its surface 51, as a result of which the shaft 30 is released by the lever L1 and begins its leftward stroke due to the effect of the tensile stress exerted by the elastic cables, which are now no longer retained, restoring the lever L1 and the wheel 14 to the positions already shown in FIG. 3. As the shaft 30 continues in its leftward displacement, the movable elements of the device return to the positions shown in FIG. 1. As mentioned previously, the force R4 overcomes the force of friction existing at the point of contact between the end 18 of the lever L2 and the surface 39 of the trigger L3, enabling the anticlockwise rotation of the trigger L3 and releasing the lever L2 that also turns anticlockwise, due to the effect of the spring M2, until it abuts against the shoulder S4.

To adjust the device, i.e. to adjust the effort needed to pull the trigger L3, reference is made to the positions shown in FIGS. 4 and 6. In the position shown in FIG. 4, the upper rear portion of the ledge 19 rests against the hub 11 at the point P1. In the position shown in FIG. 4, as in FIGS. 2 and 5, the hub 11 is in its rearmost position.

Supposing now that the threaded stem 10 is screwed down into the threaded hole in the hub 11, by means of an action taken on the knurled ring 12, until the hub 11 reaches its forwardmost position, as shown in FIG. 6, the point of contact between the hub 11 and the ledge 19 changes to P2.

It is easy to demonstrate that, moving the position of the pin C1 leftwards increases the torque needed to pull the trigger L3 by overcoming the torque of the friction generated by the force with which the end 18 of the lever L2 presses against the surface 39 of the trigger L3.

Moreover, since the upper rear part of the ledge 19 is convex, the leftward displacement of the point of contact entails a clockwise angular displacement of the lever L3 so the angular displacement required for the trigger to release the shaft 30 also increases.

Let R be the force exerted by the shaft 30 on the wheel 14 and R1 the component applied to the lever L2, the resulting moment will be M1=R1*b1, where b1 is the lever arm consisting of the distance of the line of action of the force R1 from the axis of rotation of the pin C2.

The moment M1 is balanced by the moment M2=R2*b2, where R2 is the force applied by the end 18 of the lever L2 on the surface 39, and b2 is the corresponding lever arm with respect to the axis of the pin C2.

To make the trigger L3 turn, it is consequently necessary to overcome the torque M3=R3*b3=f*R2*b3, where f indicates the coefficient of friction between the elements 18 and 39, and b3 is the radius of curvature of the circular surface 39 concentric to the axis of the pin C3. In other words, the torque that the scuba diver needs to exert on the trigger to make it turn is M4=R4*b4, where R4 indicates the force applied by the scuba diver's finger on the front surface 51 of the trigger L3 and b4 indicates the arm of said force with respect to the axis of the pin C3.

Thus, R4=R1*f*b1*b3/(b2*b4), where the only variable is the arm b1, which increases when the hub 11 is shifted leftwards, as seen in the figure, i.e. towards the front end of the gun, when the threaded stem 10 is screwed into the threaded hole in the hub 11.

It is consequently possible to vary the force required to pull the trigger, between a minimum (FIG. 4) and a maximum (FIG. 6).

It should also be noted that, when the force needed to pull the trigger is increased, the angular displacement required for the trigger to succeed in releasing the shaft 30 also increases because the extent of the sliding action of the end 18 over the surface 39 before it reaches the edge 40 of the trigger L3 is also greater.

The effect of the above-mentioned adjustment is obviously maximized when the spear shafts associated with a given gun are used, but it also allows for different shafts to be used, even if their cavity 33 differs slightly in shape or position.

Various modifications and alterations to the present invention may be appreciated based on a review of this disclosure. These changes and additions are intended to be within the scope and spirit of the invention as defined by the following claims. 

1. A device for releasing a spear shaft of a spear gun, the gun comprising a frame having a longitudinally elongated body for supporting the shaft and terminating with a grip portion and an underlying trigger connected pivotally to the frame, the elastically opposed operation of the trigger being configured so as to release a latch element engaged with a shaped recess formed in a rear end of the shaft so as to withstand a pulling force exerted axially along the shaft by an elastic member connected to the frame and providing a propulsive force launching the spear, wherein the latch element is formed on a first lever pivotally connected at its front end to a stem attached to the frame and generally parallel to the longitudinal axis, the elastic member maintaining the first lever in a resting position at which the gun is not loaded, wherein the latch element abuts a first shoulder attached to and integrally with the frame and is aligned axially relative to the shaft when it is prepared for loading in the elongated body of the frame; the trigger comprising an abutment portion forced elastically against the front end of the first lever and extending forward of a convex upper surface intersecting a concave surface at an edge which, upon rotation of the trigger, traces a first circular trajectory; a second lever being pivotally connected to the frame at a point generally behind the latch element and below the front end of the first lever, the front end of the second lever being displaceable along a second circular trajectory that intersects the first circular trajectory, an arm of the second lever extending so as to intersect the trajectory of the shaft as it is loaded in the gun, whereby upon axial movement for loading the spear, the spear shaft first abuts the latch element, thus moving the first lever away from its resting position and comes to a loaded position, wherein the latch element engages the shaped recess and abuts the arm of the second lever, causing it to rotate until it abuts the first lever at the latch element, simultaneously raising its front end up to and against the convex surface of the trigger, the front end of the first lever being slidingly connected to the stem such that the first lever is adjustably displaceable in the direction of the longitudinal axis so as to vary the point at which the first lever rests against the second lever and thereby adjust the force with which the front end of the second lever rests against the convex surface of the trigger.
 2. The release device set forth in claim 1, wherein the stem has a threaded portion screwed into a hub on which at least one swivel pin is mounted, the first lever being pivotally attached to the swivel pin.
 3. The release device according set forth in claim 2, wherein the hub is formed with a threaded through hole into which the threaded stem is screwed; the threaded stem being pivotable, through a knurled ring, in an axially fixed position between a pair of bushings.
 4. The release device set forth in claim 3, wherein the abutment portion on the trigger is a ledge projecting forwardly from its upper end, so as to support the hub.
 5. The release device set forth in claim 4, wherein the upper surface of the ledge is convex so that any variation in the axial position of the hub coincides with a variation in the angular forward-most position of the trigger and varies the angular displacement needed for the front end of the second lever to reach the edge where the convex and concave surfaces of the trigger intersect, thereby releasing the spear shaft.
 6. The release device set forth in claim 1, wherein the concave surface is formed along the rear side of the trigger and is an arc of a circle whose nominal radius is generally equal to the radius of the trajectory of the second lever's front end.
 7. The release device set forth in claim 6, wherein the convex surface is formed along the upper side of the trigger and forms an arc of a circle concentric with its axis of rotation.
 8. The release device set forth in claim 1, wherein the elastic member acting on the first lever is coaxial with the swivel pin of the second lever.
 9. The release device set forth in claim 1, wherein the trigger includes an elastic member coaxial with its swivel pin and arranged between the trigger and the first lever.
 10. The release device set forth in claim 9, wherein the first lever is pivotally mounted to a swivel pin on a hub formed with a threaded through hole into which the threaded stem is screwed, the threaded stem being pivotable in an axially fixed position between a pair bushings.
 11. The release device set forth in claim 10, wherein a ledge projects forwardly from the upper end of the trigger and acts as a support for the hub.
 12. The release device set forth in claim 11, wherein the upper surface of the ledge is convex, whereby any variation in the axial position of the hub corresponds to a variation in the angular forward-most position of the trigger and varies the angular displacement needed for the front end of the second lever to reach the edge where the convex and concave surfaces of the trigger intersect, thereby releasing the spear shaft.
 13. The release device set forth in claim 1, wherein the trigger and the second lever lie in a vertical plane containing a longitudinal axis of symmetry of the gun and the first lever comprises two halves extending generally parallel to and symmetrically with the axis and at a distance corresponding to at least the thickness of the trigger and the second lever so as to enable the free movement of the first lever relative thereto.
 14. The release device set forth in claim 1, wherein the latch element is provided at the rear end of the first lever and comprises a wheel on which the rear end of the shaft can slidingly engage.
 15. The release device set forth in claim 1, wherein a stem extends from the second lever, lying on the vertical plane of symmetry and slidingly connected to the frame, with one end configured so as to project from the frame when the device is loaded to enable the winding of a string line for the spear. 